Thermionic gaseous discharge rectifier



Patented July 30, 1940 UNITED STATES 2,209,837 'rnnamomo GASEOUS mscnsmn RECTIFIER.

James D. Le Van, Belmont, Masa, assignmto Raytheon Production Corporation, Newton, Mass, a corporation of Delaware Application October 27, 1937, Serial No. 171,291

9 Claims. (Cl. 25027.5)

This invention relates to thermionic gaseous discharge rectifiers, and more particularly to such rectifiers in which the cathode is heated to temperature of thermionic emission by means of the discharge current.

My co-pending application, Serial No. 8,464, filed February 27, 1935, describes and broadly claims such a rectifier.

An object of this invention is to devise a. struc- 19 ture whereby the life of the cathode of rectifiers of this kind may be increased.

Another object is to produce an arrangement in which the assembling of the rectifier is facilitated.

15 A further object is to produce a structure in which the sealing of the anodes and their associated shields into the stem is facilitated.

A still further object is to provide means for decreasing the noise which such a rectifier tends go to introduce into an associated radio set.

The foregoing and other objects of this invention will be best understood from the following description of an embodiment thereof, wherein:

Fig. l is a cross-sectional elevation of one of my novel tubes;

Fig. 2 is a side view of the stem and electrode structure carried thereby;

Fig. 3 is a perspective view of the stem structure shown in Fig. 2; and

30 Fig. 4 is a cross-sectional view of the anode and associated shield structure taken along a line at right angles to the plane of Fig. 1.

In the drawing is shown a rectifier consisting of a glass envelope l having a reentrant stem 2 35 at the upper end of which is formed a press 3. The tube may be filled with an ionizable gas at a pressure suificiently high to produce copious ionization therethrough upon the passage of a discharge.

40 of such gases at a pressure of about four to five millimeters of mercury. More particularly I prefer to use argon at the above pressure.

The press 3 is formed with a main portion 4 at the ends of which are disposed the transverse 45 wing members 5. The wing members 5 extend from the ends of the main portion 4 at an angle thereto so as to provide supporting press members transversely beyond the ends of the main portion d.

50 The rectifier is provided with two anode structures 6 each surrounded by a metallic anode shield I. The maximum distance between the interior of the shield I and the exterior of the anode structure is sufdciently small so that a discharge 55 will not ordinarily occur in the space between I prefer to. use a rare gas or a mixture these elements. The lower ends of the anode structure 6 and of the shield I are sealed in the main stem portion 4. The structure of the anodes and their associated shields is more fully described and claimed in my co-pending application *5 referred to above. In said application it is pointed out wherein it is desirable that the lower end 8 of the anode structure 6 is disposed in the press at a lower level than the lower end of the shield I. This arrangement has introduced dif- 1c ficulties in producing a good seal between, the glass of the press and the lower ends of the shield and of the anode structure without crushing the lower ends of the shields. I have devised a press structure which eliminates this difficulty and which produces satisfactory seals even on a mass production basis. In order to produce this result the main portion 4 of the press 3 is formed with a thickened upper portion 9 and a lower portion Ill of decreased thickness. The portion 9 extends substantially along the shield I to a point slightly below the lower end thereof. The thinner portion l0 extends to a substantial degree along the lower end 8 of the anode structure 6. It will be noted that the thickness of glass between the outside of the shield and the outside of the stem is substantially the same as the thickness of glass between the outside of the lower end 8 of the anode structure 6 and the outside of the stem. An anode lead II is connected to the lower end 8 of each anode 6 so as to provide an external electrical connection.

By the foregoing construction the stem described may be formed by the usual stem-making machine in which anvils or press members are shaped so as to produce the two different thicknesses of glass 9 and 89. When the relationships described are produced, substantially the same pressure of glass against metal is exerted in the case of the lower end of the shield i and also the M lower end 8 of the anode structure 6. Under these conditions I have found that good seals are consistently produced.

In order to support the cathode of the rectifier,

a cathode lead l2 is sealed in each of the wing members 5. As will beseen most clearly in Fig. 2, due to the fact that the wings 5 extend outwardly from the ends of the main stem portion 4, the cathode leads I! emerge from the wing members 5 at a point where they lie transversely beyond the shields I of the anode structures 6. Welded to the upper end of each cathode lead it is a cathode-supporting strip l3. Each of these strips I3 is made of an electrical conductor having a relatively low heat conductivity so that heat is not readily conducted away from the emitting portion of the cathode structure. The emitting portion of the cathode structure is formed by a plurality of cathode ribbons l4. Each of these cathode ribbons H is welded at its opposite ends to the cathode-conducting strips l3, and in this way the cathode ribbons are connected in parallel with each other. Each cathode ribbon is preferably formed of a thin strip of platinum irridium having an electron-emissive coating burned onto the surface thereof. This coating may be the barium, strontium, oxide coating described in my co-pending application mentioned above. As set forth in said application, the ribbons l3 preferably are of a thickness of the order of magnitude of .0006 inch, and are likewise preferably of the order of .010 inch wide.

The lateral displacement of the cathode leads l2. beyond the shields I and the location of said leads l2 in a difierent plane than that in which the anodes 6 lie produce a structure which is readily fabricated. Suilicient space is thus created so that a welding tool can be brought up in contact with the cathode lead I2 without interference by the shield 1, whereby the cathodesupporting strips l3 may be welded readily to the cathode leads i2. Likewise, such a welding tool can be brought up into contact with the cathodesupporting strips l3 without interference from the shields I so that the cathode ribbons H may be welded to said strips. Furthermore, due to the fact that by this arrangement the ribbons ll lie in a different plane from tli'at in which the anodes 5 lie, the ribbons can be stretched between the two cathode-supporting strips I3. Since the ribbons M are formed of such thin material, as described above, it becomes important that handling of this relatively fragile material be facilitated during the assembling operation. Due to the structure described above, such cathode ribbons H can readily be handled with a minimum amount of spoilage.

As described in said co-pending application, the initiation of a discharge between the anodes and the cathode causes the coated ribbons H to be heated to temperature of thermionic emission. Since'during the initiation of such a discharge the action is sometimes destructive to the cathode, there is a tendency for one or more of the oathode ribbons M to be burned through during the lifetime of the tube. Due to the fact that any desired number of cathode ribbons H can be utilized in the construction which I have described, one or more of the cathode ribbons I4 cannot only be burned through but can be com-- pletely consumed without terminating the life of the tube, due to the fact that additional ribbons M are provided to furnish an active cathode element. Thus, by increasing the number of cathode ribbons M, the life of the cathode and likewise the life of the tube can be extended substantially. The low conductivity of the cathodesupporting stn'ps l3 decreases the loss of heat from the cathodes, and thus permits the cathodes to be raised to their operating temperature in a shorter length of time. This likewise tends to increase the iife of the tube.

The main press portion 4 may likewise be provided with a getter standard l5 upon which is supported a getter plate It. Any suitable getter l'l may be secured to the getter plate for the wellknown purpose of gettering the tube. The reentrant stem 2 is likewise provided with the usual exhaust tube I 8.

The tube described above may be provided with the insulating base I8 in which are supported conducting base plus 20. The two anode leads II are connected to two of the base pins while the two cathode leads I2 are connected to one of the base pins 20. The insulating base I9 is supported with a centering plug 2| having an orienting feather 22 formed thereon.

Such a tube as I have described above tends to produce disturbances within the gas. When the rectifier is used with sensitive radio-receiving sets.

these disturbances if permitted to be fed into saic set tend to produce noises. I have found, however, that if the tube described is surrounded with a metallic envelope, these disturbances are effectively prevented from escaping from the tube, and thus the tube may be used safely in sensitive radio-receiving sets without introducing any substantial amount of noise therein.

The tube therefore is provided with a metal shell 23 which is welded at its lower end to a metal ring 24. The shell 23 and ring 24 are maintained in place around the glass envelope i, and also retain the insulating base IS in place with respect to said glass envelope l by having portions 25 of the ring 24 indented into corresponding recesses 28 in the insulating base IS. The metal shell 23 has connected thereto a conductor 28 which is likewise connected to one of the base pins 20, whereby the shell 23 is adapted to be connected to ground. It is desirable to resiliently support the glass envelope l within the metal shell 23, and for this reason resilient spacers 21 are interposed between the upper end of the glass envelope I and the corresponding upper walls of the metal shell 23. These resilient spacers are preferably formed of resilient plates of mica. The lead-in wires ll, l2 and 28 possess in themselves a certain amount of resiliency so that the glass envelope l is resiliently supported within the surrounding shell structure by means of the lead-in wires as well as the resilient spacers 2i. i

This invention is not limited to the particular details of construction as described above inasmuch as those skilled in the art will readily perceive various equivalents which can be used. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the present invention within the art.

What is claimed is:

1. An electrical space discharge device comprising an envelope containing an ionizable gas, a reentrant glass presscarrying electrodes adapted to support an ionizing discharge through said gas, one of said electrodes being a rod-shaped anode sealed in said press, and a conducting shield of larger diameter than said anode surrounding said anode, said shield being also sealed in said press, the lower end of said shield being at a higher level than the lower end of said anode, said press being of a certain thickness adjacent the region into which the lower end of said shield projects, and being of a decreased thickness adjacent the region where the lower end of said anode projects beyond the lower end of said shield.

2. An electrical space discharge device comprising an envelope containing an ionizable gas, a reentrant glass press carrying electrodes adapted to support an ionizing discharge through said gas, one of said electrodes being a rodshaped anode sealed in said press, and a conducting shield of larger diameter than said anode surrounding said anode, said shield also being sealed in said'press, the lower end of saidshield being at a higher level than the lower end of said anode, said press being of a certain thickness adjacent the region into which the lower end of said shield projects, and being of a decreased thickness adjacent the region where the lower end of said anode projects beyond the lower end of said shield, the thickness of glass between the shield and the outside of said press being substantially, equal to the thickness of glass between the lower end of said anode and the outside of said press.

3. An electrical space discharge device comprising an envelope containing a gas filling, a reentrant glass press carrying electrodes adapted to support an ionizing discharge through said gas, said press having a main portion disposed in one plane, a plurality of rod-shaped anodes sealed in said main portion, said press having formed at each end of said main portion a wing portion projecting outwardly at an angle to said main portion, a cathode-supporting conductor sealed in each of said wing portions, said conductors lying in another plane from that of said anodes, and a cathode-emissive element extending between said conductors and securely fastened thereto.

4. An electrical space discharge device comprising an envelope containing a gas filling, a reentrant. glass press carrying electrodes adapted to support an ionizing discharge through said gas,

said press having a main portion disposed in one plane, a plurality of rod-shaped anodes sealed in saidmain portion, said press having formed at each end of said main portion a wing portion projecting outwardly at an angle to said main portion, a cathode-supporting conductor sealed in each of said wing portions, said conductors lying in another plane from that of said anodes, said conductors also being disposed laterally beyond the outermost anodes, and a cathodeemissive element extending between said conductors and securely fastened thereto. 5. An electrical space discharge device comprising an envelope containing an ionizable gas, electrodes adapted to support an ionizing discharge through said gas, one of said electrodes being a thermionic cathode, said cathode comprising a plurality of conductors, each of which has an electron-emitting surface and is adapted to be heated to temperature of thermionic emission solely by the discharge, and two cathodesupporting leads mounted in said envelope, each of said conductors being connected between said supporting leads, and said supporting leads being directly connected to each other, whereby all of said conductors are connected in parallel with a single common external electrical connection thereto.

6. An electrical space discharge device comprising an envelope containing an ionizable gas,

said support being of a certain thickness adjacent.

the region into which the lower end of said shield projects, and being of a decreased thickness adjacent the region where the lower end ofsaid anode projects beyond the inner end of said shield.

7. An electrical space discharge device comprising an envelope containing an ionizable gas,

. a glass support carrying electrodes adapted to support an ionizing discharge through said gas, one of said electrodes being a rod-shaped anode sealed in said support, a conducting shield of larger diameter than said anode surrounding said anode, said shield being also sealed in said sup-' port, the lower end of said shield being at a higher level than the lower end of said anode, said support being of a certain thickness adjacent the region into which the lower end of said shield projects, and being of a decreased thickness adjacent the region where the lower end of said anode projects beyond the inner end of said shield, the thickness of glass between the shield and the outside of said support being substantially equal to the thickness of glass between the lower end of said anode and the outside of said support.

8. An electrical space discharge device comprising an envelope containing an ionizable gas, a glass support carrying electrodes adapted to support an ionizing discharge through said gas, said electrodes including a plurality of rod-shaped anodes sealed in said support, a plurality of cathode-supporting conductors sealed in said sup-' port, said conductors lying in another plane from that of said anodes, and a filamentary cathodeemissive element extending between said conductors and securely fastened thereto.

9. An electrical space discharge device comprising an envelope containing an ionizable gas, a glass support carrying electrodes adapted to support an ionizing discharge through said gas, said electrodes including a plurality of rod-shaped anodes sealed in said support, a plurality of cathode-supporting conductors sealed in said support, said conductors lying in another plane from that of said anodes, said conductors also being disposed laterally beyond the outermost anodes, and a filamentary cathode-emissive element extending between said conductors and securely fastened thereto.

JAMIS D. LE VAN. 

